Lithographic apparatus and device manufacturing method

ABSTRACT

In a single or multiple stage lithography apparatus, a table provides a confining surface to a liquid supply system during, for example, substrate table exchange and/or substrate loading and unloading. In an embodiment, the table has a sensor to make a measurement of the projection beam during, for example, substrate table exchange and/or substrate loading and unloading.

FIELD

The present invention relates to a lithographic apparatus and a methodfor manufacturing a device.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. The point of this is to enableimaging of smaller features since the exposure radiation will have ashorter wavelength in the liquid. (The effect of the liquid may also beregarded as increasing the effective numerical aperture (NA) of thesystem and also increasing the depth of focus.) Other immersion liquidshave been proposed, including water with solid particles (e.g. quartz)suspended therein.

However, submersing the substrate or substrate and substrate table in abath of liquid (see, for example, U.S. Pat. No. 4,509,852, herebyincorporated in its entirety by reference) means that there is a largebody of liquid that must be accelerated during a scanning exposure. Thisrequires additional or more powerful motors and turbulence in the liquidmay lead to undesirable and unpredictable effects.

One of the solutions proposed is for a liquid supply system to provideliquid on only a localized area of the substrate and in between thefinal element of the projection system and the substrate using a liquidsupply system (the substrate generally has a larger surface area thanthe final element of the projection system). One way which has beenproposed to arrange for this is disclosed in PCT patent application WO99/49504, hereby incorporated in its entirety by reference. Asillustrated in FIGS. 2 and 3, liquid is supplied by at least one inletIN onto the substrate, preferably along the direction of movement of thesubstrate relative to the final element, and is removed by at least oneoutlet OUT after having passed under the projection system. That is, asthe substrate is scanned beneath the element in a −X direction, liquidis supplied at the +X side of the element and taken up at the −X side.FIG. 2 shows the arrangement schematically in which liquid is suppliedvia inlet IN and is taken up on the other side of the element by outletOUT which is connected to a low pressure source. In the illustration ofFIG. 2 the liquid is supplied along the direction of movement of thesubstrate relative to the final element, though this does not need to bethe case. Various orientations and numbers of in- and out-letspositioned around the final element are possible, one example isillustrated in FIG. 3 in which four sets of an inlet with an outlet oneither side are provided in a regular pattern around the final element.

To maintain the performance of a lithographic apparatus, periodicmeasurements of the performance of the radiation source, illuminationsystem and projection system may be taken so that corrective measures,such as recalibrations, can be taken if there is any degradation in theperformance of any part of the apparatus. One or more sensors may beprovided in the optical path of the apparatus to measure one or moreparameters that may affect imaging but it is desired, and in some casesessential, to take measurements at substrate level and directly in theaerial image. Such measurements cannot be done concurrently with and atthe same as production exposure so that periodic downtime is provided,reducing the throughput of the apparatus.

SUMMARY

Accordingly, it would be advantageous, for example, to provide alithographic apparatus in which a measurement at substrate level may beperformed without reduction in throughput.

According to an aspect of the invention, there is provided a positioningapparatus for use in a lithographic apparatus for projecting a patternedbeam of radiation onto a substrate, the positioning apparatuscomprising:

a first table connected to a first positioning system configured todisplace the first table into and out of a path of the patterned beam ofradiation, the first table being configured to hold a substrate; and

a second table connected to a second positioning system configured toposition the second table into the path of the patterned beam ofradiation when the first table is displaced out of the path of thepatterned beam of radiation, the second table not being configured tohold a substrate.

According to an aspect of the invention, there is provided alithographic apparatus, comprising:

a substrate table configured to hold a substrate;

a projection system configured to project a patterned beam of radiationonto the substrate;

a first positioning system connected to the substrate table andconfigured to displace the substrate table into and out of a path of thepatterned beam of radiation;

a sensor table not configured to hold a substrate and comprising asensor configured to sense a property of the patterned beam ofradiation; and

a second positioning system configured to position the sensor table intothe path of the patterned beam of radiation when the first table isdisplaced out of the path of the patterned beam of radiation.

According to another aspect of the invention, there is provided a devicemanufacturing method, comprising:

projecting a patterned beam of radiation onto a substrate held on atable;

displacing the table out of a path of the patterned beam of radiation;and

moving a sensor into the path of the patterned beam of radiation andmeasuring a property of the beam, the moving of the sensor and themeasuring of the property occurring at least partly concurrently withthe displacing of the table.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts another liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a liquid supply system for use in a lithographicapparatus according to an embodiment of the invention;

FIG. 6 depicts measurement and exposure stations of an embodiment of theinvention; and

FIG. 7 is a view similar to FIG. 6 but showing the situation duringtable exchange.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam PB (e.g. UV radiation or DUV radiation).    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device in accordance with certain parameters;    -   a substrate table (e.g. a wafer table) WT constructed to hold a        substrate (e.g. a resist-coated wafer) W and connected to a        second positioner PW configured to accurately position the        substrate in accordance with certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PL configured to project a pattern imparted to the radiation        beam PB by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The support structure holds the patterning device in a manner thatdepends on the orientation of the patterning device, the design of thelithographic apparatus, and other conditions, such as for examplewhether or not the patterning device is held in a vacuum environment.The support structure can use mechanical, vacuum, electrostatic or otherclamping techniques to hold the patterning device. The support structuremay be a frame or a table, for example, which may be fixed or movable asrequired. The support structure may ensure that the patterning device isat a desired position, for example with respect to the projectionsystem. Any use of the terms “reticle” or “mask” herein may beconsidered synonymous with the more general term “patterning device”.

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more support structures). In such“multiple stage” machines, the additional tables may be used inparallel, or preparatory steps may be carried out on one or more tableswhile one or more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam PB is incident on the patterning device (e.g., maskMA), which is held on the support structure (e.g., mask table MT), andis patterned by the patterning device. Having traversed the patterningdevice MA, the radiation beam PB passes through the projection systemPL, which focuses the beam onto a target portion C of the substrate W.With the aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam PB.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamPB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

-   -   1. In step mode, the support structure MT and the substrate        table WT are kept essentially stationary, while an entire        pattern imparted to the radiation beam is projected onto a        target portion C at one time (i.e. a single static exposure).        The substrate table WT is then shifted in the X and/or Y        direction so that a different target portion C can be exposed.        In step mode, the maximum size of the exposure field limits the        size of the target portion C imaged in a single static exposure.    -   2. In scan mode, the support structure MT and the substrate        table WT are scanned synchronously while a pattern imparted to        the radiation beam is projected onto a target portion C (i.e. a        single dynamic exposure). The velocity and direction of the        substrate table WT relative to the support structure MT may be        determined by the (de-)magnification and image reversal        characteristics of the projection system PL. In scan mode, the        maximum size of the exposure field limits the width (in the        non-scanning direction) of the target portion in a single        dynamic exposure, whereas the length of the scanning motion        determines the height (in the scanning direction) of the target        portion.    -   3. In another mode, the support structure MT is kept essentially        stationary holding a programmable patterning device, and the        substrate table WT is moved or scanned while a pattern imparted        to the radiation beam is projected onto a target portion C. In        this mode, generally a pulsed radiation source is employed and        the programmable patterning device is updated as required after        each movement of the substrate table WT or in between successive        radiation pulses during a scan. This mode of operation can be        readily applied to maskless lithography that utilizes        programmable patterning device, such as a programmable mirror        array of a type as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets IN oneither side of the projection system PL and is removed by a plurality ofdiscrete outlets OUT arranged radially outwardly of the inlets IN. Theinlets IN and OUT can be arranged in a plate with a hole in its centerand through which the projection beam is projected. Liquid is suppliedby one groove inlet IN on one side of the projection system PL andremoved by a plurality of discrete outlets OUT on the other side of theprojection system PL, causing a flow of a thin film of liquid betweenthe projection system PL and the substrate W. The choice of whichcombination of inlet IN and outlets OUT to use can depend on thedirection of movement of the substrate W (the other combination of inletIN and outlets OUT being inactive).

Another immersion lithography solution with a localized liquid supplysystem solution which has been proposed is to provide the liquid supplysystem with a liquid confinement structure which extends along at leasta part of a boundary of the space between the final element of theprojection system and the substrate table. The liquid confinementstructure is substantially stationary relative to the projection systemin the XY plane though there may be some relative movement in the Zdirection (in the direction of the optical axis). A seal is formedbetween the liquid confinement structure and the surface of thesubstrate. In an embodiment, the seal is a contactless seal such as agas seal. Such a system with a gas seal is disclosed in U.S. patentapplication Ser. No. 10/705,783, hereby incorporated in its entirety byreference.

FIG. 5 shows a liquid supply system comprising a liquid confinementstructure (sometimes referred to as an immersion hood or showerhead)according to an embodiment of the invention. In particular, FIG. 5depicts an arrangement of a reservoir 10, which forms a contactless sealto the substrate around the image field of the projection system so thatliquid is confined to fill a space between the substrate surface and thefinal element of the projection system. A liquid confinement structure12 positioned below and surrounding the final element of the projectionsystem PL forms the reservoir. Liquid is brought into the space belowthe projection system and within the liquid confinement structure 12.The liquid confinement structure 12 extends a little above the finalelement of the projection system and the liquid level rises above thefinal element so that a buffer of liquid is provided. The liquidconfinement structure 12 has an inner periphery that at the upper endpreferably closely conforms to the shape of the projection system or thefinal element thereof and may, e.g., be round. At the bottom, the innerperiphery closely conforms to the shape of the image field, e.g.,rectangular though this need not be the case.

The liquid is confined in the reservoir by a gas seal 16 between thebottom of the liquid confinement structure 12 and the surface of thesubstrate W. The gas seal is formed by gas, e.g. air, synthetic air, N₂or an inert gas, provided under pressure via inlet 15 to the gap betweenliquid confinement structure 12 and substrate and extracted via outlet14. The overpressure on the gas inlet 15, vacuum level on the outlet 14and geometry of the gap are arranged so that there is a high-velocitygas flow inwards that confines the liquid. It will be understood by theperson skilled in the art that other types of seal could be used tocontain the liquid such as simply an outlet to remove liquid and/or gas.

FIG. 6 shows substrate stage arrangements according to an embodiment ofthe invention. The embodiment is a so-called dual stage apparatus inwhich at substrate level there are two stations: an exposure station ESand a measurement station MS. At the exposure station, substrates areexposed while at the measurement station various measurements arecarried out, for example, to characterize a substrate prior to exposureor to verify that exposure has been carried out correctly. One or moresensors may be provided at the measurement station to perform themeasurements and examples of the types of a sensor that may be providedat the measurement station include a level sensor LS to make a heightmap of a substrate prior to exposure, an alignment sensor AS to measurethe position of one or more alignment markers on the substrate, and ascatterometer SM to examine the latent image of an exposed substrate. Aload/unload robot (not shown) is also provided to load and unloadsubstrates to a substrate table at the measurement station. In such adual stage apparatus, while one substrate is being exposed, a previouslyexposed substrate can be measured and/or a next substrate to be exposedcan be pre-measured. A dual stage apparatus therefore can have improvedthroughput as compared to a single stage apparatus in which bothmeasurement and exposure steps are carried out at a single station.

Referring to FIG. 6, the apparatus has two substrate tables WT1, WT2which are positioned by a positioning system PW comprising two H-drives,each to position a substrate table within one of the stations. As shownin FIG. 7, according to an embodiment, at the end of an exposureprocess, the two substrate tables WT1, WT2 are positioned at theboundary between the two stations and decoupled from the positioningsystem PW; each H-drive then pick-ups the substrate table released bythe other H-drive. This procedure is sometimes referred to as a chuckswap or table exchange. Thus, the substrate W2 that has just beenpre-measured at the measurement station can be exposed at the exposurestation and the substrate W1 that has just been exposed can be measuredand/or unloaded at the measurement station. An alternative arrangementhas two measurement stations and two substrate tables but a singleexposure station. Each substrate table is positioned by a drive systemhaving a range including its own measurement station and the exposurestation so that there is no exchange of tables between parts of thepositioning system. However, there is still a period which may bereferred to as table exchange during which one table is moving out ofthe exposure station and the other one is moving in.

In an immersion lithography apparatus with a localized liquid supplysystem, e.g. of the showerhead type, during the table exchange procedurethe liquid supply system will be turned off or a closing surfaceprovided to prevent immersion liquid from leaking into the remainder ofthe apparatus. In an embodiment, a closing plate may be provided in arecess on the substrate table from which it is picked up by a liquidconfinement structure IH before the substrate table is moved out fromunder the projection system PL.

In an embodiment of the invention, a third table 21 is provided, with apositioning system 22, 23 that is capable of positioning the third tableunder the projection system PL and liquid confinement structure IH. Thethird table 21 and the positioning system 22, 23 may together form thethird stage 20. The third table 21 may fulfill at least two functions.Firstly, it can provide a confining surface at the bottom of the liquidconfinement structure IH when the substrate table WT1, WT2 is removed toprevent the immersion liquid leaking out into the remainder of theapparatus. Secondly, the third table 21 may comprise a sensor unit 24comprising one or more sensors to make a measurement of the aerial imageprojected by the projection system PL. Types of sensor that can beincluded in the sensor unit include a transmission image sensor (TIS),an energy sensor, a polarization sensor and a shearing interferometersensor (see, for example, U.S. patent application Ser. No. 10/988,845,filed Nov. 16, 2004, which document is hereby incorporated in itsentirety by reference). In an embodiment, the sensor unit 24 mayadvantageously include a shearing interferometer sensor, which is usedto characterize aberrations in the projection system PL, since themeasurements taken by such a sensor take a comparatively long time andare important to imaging performance.

By providing the sensor unit to a third table 21, the sensor(s) cantherefore be used to make a measurement at substrate level withoutreducing throughput by making use of the substrate table exchangeinterval. The reduction in downtime achievable may therefore besubstantial. It should be noted that if the desired measurement(s)(e.g., measurements necessary for a calibration) takes longer than thetime taken for substrate table exchange, the measurement(s) may be splitinto several parts and performed during several substrate table exchangeperiods, possibly with modifications to account for factors that maychange over the period between measurements. Alternatively or inaddition, the exchange period may be extended to accommodate themeasurement(s) on one or more occasions causing some loss of throughput,but less than if the whole measurement were carried out during asubstrate exposure downtime.

An advantage also accrues from providing a polarization sensor as partof the sensor unit on the third table as a polarization sensor can bequite bulky, involving several optical components, and therefore may bedifficult to accommodate on one or both of the substrate tables WT1,WT2.

Depending, for example, on the type of sensor provided to the thirdtable 21, the positioning system 22, 23 may comprise simply a longstroke drive module to position the third table 21 under the projectionsystem PL, as shown in FIG. 7, in synchronism, for example, with theremoval of the substrate table WT1, WT2. This may be carried out undercontrol of a controller CS connected to the positioning system of thethird table 21 and the positioning system of the substrate table WT1,WT2. Optionally, a short stroke drive module may be included if thesensor requires more accurate positioning and/or scanning to make themeasurement. Where more than one sensor is provided, the sensors may befitted into the area of the exposure field so as to operatesimultaneously or if that is inconvenient, the positioning system may bearranged to position different sensors in the exposure fieldsuccessively.

It should be noted that while the invention has been described inrelation to a dual stage immersion type lithographic apparatus, it mayalso be used with non-immersion apparatus and with a single stageapparatus where the substrate table is moved out from under theprojection system for substrate loading and unloading operations. Thethird table may also be provided with other devices, e.g. a cleaningdevice configured to cleaning a final element of the projection system,in addition to or instead of the sensor. The cleaning device may usegas, electric particles, a laser or other mechanisms for cleaning theprojection system. A third table may also be used in an immersionlithography apparatus without a sensor or other device and rather simplyto provide a confining surface for the liquid supply system during, forexample, table exchange and/or substrate loading and unloading.

Further, a multiple (e.g., two) stage lithographic apparatus (with orwithout immersion capability) may comprise one exposure station and morethan one measurement station. In this arrangement, for example, ameasurement station may be provided on opposite sides of an exposurestation, where the projection system is positioned, and then twosubstrate tables may be shuttled between the two measurement stationsand the exposure station. As an example, a first substrate table may beshuttled between the exposure station and a first measurement stationand the second substrate table may be shuttled between the exposurestation and a second measurement station. In an implementation, the twosubstrate tables may be shuttled in tandem back and forth so that thefirst substrate table only moves between the exposure station and afirst measurement station and the second substrate table moves onlybetween the exposure station and a second measurement station.

In European Patent Application No. 03257072.3, the idea of a twin ordual stage immersion lithography apparatus is disclosed. Such anapparatus is provided with two tables for supporting a substrate.Leveling measurements are carried out with a table at a first position,without immersion liquid, and exposure is carried out with a table at asecond position, where immersion liquid is present. Alternatively, theapparatus has only one table.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm).

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, including refractiveand reflective optical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the invention may take the form of acomputer program containing one or more sequences of machine-readableinstructions describing a method as disclosed above, or a data storagemedium (e.g. semiconductor memory, magnetic or optical disk) having sucha computer program stored therein.

One or more embodiments of the present invention may be applied to anyimmersion lithography apparatus, such as those types mentioned above,and whether the immersion liquid is provided in the form of a bath oronly on a localized surface area of the substrate. A liquid supplysystem is any mechanism that provides a liquid to a space between theprojection system and the substrate and/or substrate table. It maycomprise any combination of one or more structures, one or more liquidinlets, one or more gas inlets, one or more gas outlets, and/or one ormore liquid outlets, the combination providing and confining the liquidto the space. In an embodiment, a surface of the space may be limited toa portion of the substrate and/or substrate table, a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1. A positioning apparatus for use in a lithographic apparatus forprojecting a patterned beam of radiation onto a substrate, thepositioning apparatus comprising: a first table connected to a firstpositioning system configured to displace the first table into and outof a path of the patterned beam of radiation, the first table beingconfigured to hold a substrate; and a second table connected to a secondpositioning system configured to position the second table into the pathof the patterned beam of radiation when the first table is displaced outof the path of the patterned beam of radiation, the second table notbeing configured to hold a substrate and comprising a sensor configuredto sense a property of the patterned beam of radiation.
 2. The apparatusaccording to claim 1, wherein the sensor is selected from the groupcomprising: an energy sensor, a transmission image sensor, apolarization sensor, and a shearing interferometer sensor.
 3. Theapparatus according to claim 1, further comprising a liquid supplysystem configured to supply a liquid to a space between a projectionsystem and the substrate, and wherein the second table provides asurface to at least partly bound the space when the first table isdisplaced out of the path of the patterned beam of radiation.
 4. Theapparatus according to claim 1, further comprising a controllerconnected to the first and second positioning systems and configured tocontrol the respective positioning systems to position the second tableinto the path of the patterned beam of radiation in synchronism withdisplacement of the first table out of the path of the patterned beam ofradiation.
 5. The apparatus according to claim 1, wherein the secondpositioning system comprises a long stroke module and a short strokemodule, the short stroke module having a smaller range of movement but ahigher precision than the long stroke module.
 6. The apparatus accordingto claim 1, further comprising: a third table configured to hold asubstrate; an exposure station at which a substrate carried by eitherone of the first and third tables can be exposed; and a measurementstation at which a substrate carried by either one of the first andthird tables can be measured, wherein the first positioning system isconfigured to exchange the first and third tables between themeasurement station and the exposure station.
 7. The apparatus accordingto claim 1, further comprising: a third table configured to hold asubstrate; an exposure station at which a substrate carried by eitherone of the first and third tables can be exposed; and first and secondmeasurement stations at which a substrate carried by either one of thefirst and third tables can be measured, wherein the first positioningsystem is configured to exchange the first and third tables between theexposure station and the respective one of the measurement stations. 8.The apparatus according to claim 1, wherein the second table has mountedthereon a cleaning device configured to clean a projection system of thelithographic apparatus.
 9. A lithographic apparatus, comprising: asubstrate table configured to hold a substrate; a projection systemconfigured to project a patterned beam of radiation onto the substrate;a first positioning system connected to the substrate table andconfigured to displace the substrate table into and out of a path of thepatterned beam of radiation; a sensor table not configured to hold asubstrate and comprising a sensor configured to sense a property of thepatterned beam of radiation; and a second positioning system configuredto position the sensor table into the path of the patterned beam ofradiation when the substrate table is displaced out of the path of thepatterned beam of radiation.
 10. The apparatus according to claim 9,further comprising a liquid supply system configured to supply a liquidto a space between a projection system and the substrate, and whereinthe sensor table provides a surface to at least partly bound the spacewhen the substrate table is displaced out of the path of the patternedbeam of radiation.
 11. The apparatus according to claim 9, furthercomprising a controller connected to the first and second positioningsystems and configured to control the respective positioning systems toposition the sensor table into the path of the patterned beam ofradiation in synchronism with displacement of the substrate table out ofthe path of the patterned beam of radiation.
 12. The apparatus accordingto claim 9, wherein the sensor is selected from the group comprising: anenergy sensor, a transmission image sensor, a polarization sensor, and ashearing interferometer sensor.
 13. The apparatus according to claim 9,further comprising: a further substrate table configured to hold asubstrate; an exposure station at which a substrate carried by eitherone of the substrate table and the further substrate table can beexposed; and a measurement station at which a substrate carried byeither one of the substrate table and the further substrate table can bemeasured, wherein the first positioning system is configured to exchangethe substrate table and the further substrate table between themeasurement station and the exposure station.